The invention relates to an apparatus for the construction of fan wheels of the double-aspirator type, consisting essentially of a plurality of inclined blades arranged on a cylindrical surface, a pair of blade restraining end rings and at least one central disk keyed to the blades and carrying the fan wheel hub.
The construction of fan wheels, at present, requires numerous manual phases which not only limit the production possibilities but also increase the costs of the finished product. Essentially, the known technique comprises the formation, by sheet blanking, of the single blades, opportunely shaped with a base or foot determining the pitch of the same, and the assembling of the formed blades on an equipment provided for detaining them temporarily in the final assembly position according to a cylindrical surface. Subsequently, two shaped rings are fixed to the end of the blades with one end bend down to be flanged to the stem of the blade so as to form a self-supporting structure from which the temporary equipment is now extracted. Finally, a central disk is inserted into the self-supporting structure. This disk is provided with notches for the blades. The notches are forced onto the said blades by means of a further pressing operation in axial direction to the periphery of the said central disk. These operations as outlined and carried out by known means, require the expenditure of much labor for assembling the blades on the equipment, the transfer of the equipment and blades to the flanging device, the extraction of the equipment, the insertion of the central disk and the transfer of the fan wheel to the device allowing the pressing and keying on of the disk.
According to the U.S. Pat. No. 2,651,830, this cycle is, in part, mechanised by using a conveyor belt carrying the blades at a prefixed distance equal to the blade pitch, with the blades then automatically loaded onto a rotating device carrying also the central disk. This solution, though ensuring a certain reduction of the required labor, still requires the transfer of the equipment with the assembled blades and the central disk to a separate flanging device; in addition, the said disk is not keyed onto the blades so that its connection with the blade structure and the terminal rings does not ensure the required stability and stiffness values.
U.S. Pat. No. 3,305,912 proposes a machine for the automatic construction of fan wheels, in which the blanked blades are fed to an equipment assembles on a mobile rotating spindle for transporting the equipment with the assembled blades to the subsequent flanging cycle. However, this machine is designed only for the making of single aspirator effect fan wheels without any problem regarding the arrangement of the central disk, the hub of the fan wheel being integral part of one of the outer rings.
This being the state of the actual art, this invention proposes an apparatus allowing to make fan wheels of the above-mentioned type requiring only a minimum use of labor or even no labor at all while, at the same time, avoiding the troublesome transfer of the fan wheels during the working phases, together with the supporting equipment for the temporary restraining of the blades in the various working stations.